1. Field of the Invention
The present invention relates to a unit for air flow regulation in pneumatic systems. In particular, the unit implements the so-called progressive-starting regulation in an innovative manner.
2. State of the Prior Art
In pneumatically-operated machines it is always preferred for the compressed air to be gradually supplied on starting of the machine in order to prevent the pneumatic actuators from carrying out sudden movements that are potentially dangerous both for the machine structure and still more for people.
For the purpose, in the known art feeding valves (also called “APR” valves) have been proposed that on opening, gradually and automatically increase the air passage by means of a variable throttling disposed along the feeding line and, therefore, by a flow-rate regulation. The resulting pressure regulation therefore depends on the air request taking place at that moment downstream of the regulator and consequently it is not constant. The behavior of a known progressive starter can therefore be very different at each starting, because in the same machine on switching on, the different pneumatic actuators can be disposed at any position, depending on the actuator state at the moment of a preceding shutting off on occurrence of possible handling operations carried out manually. The intervention velocity of the starter usually takes place in a manner gauged for a medium case, taking into account the average of the air requests of the different actuators in the circuit, for example.
However, in this case the risks of sudden movements of some actuators are not prevented.
For instance, in the rather frequent case of the presence in the same machine of a plurality of actuators of big volume and some actuators of much smaller volume (i.e. in which a relatively reduced air amount is required for supplying wide movements), it may sometimes happen that on switching on, the bigger actuators are already at the end of their stroke and therefore do not move, so that the whole air fed by the regulator acts on one or more of the small actuators to move them, and therefore said small actuators can immediately have an air amount sufficient to produce a wide and quick movement which is potentially dangerous.
There is also a further problem. Since known regulators have a “trigger” point that makes them pass from a throttled feeding to a full and operating feeding of the circuit when a predetermined pressure has been reached downstream of said regulators, it may happen that in case of small leakages in the downstream circuit this trigger pressure is never reached and therefore the machine never succeeds in reaching the operating condition, even if losses by themselves would be negligible during normal operation.
It is a general aim of the present invention to obviate the above mentioned drawbacks by providing a regulating unit for progressive starting which is able to supply a satisfactory progressive starting irrespective of the conditions of the circuit downstream thereof. It is a further aim to supply a regulator which is also able to operate as a piloted regulator.